agrafix

This plugin adds hyperlinks to specified words in posts and pages. This can be very usefull if you are using complicated words and want to link Wikipedia articles or 
if you just want to improve your seo by linking some interessting words 🙂
<h3>Example</h3>
Your Text: 
 Welcome to a blog about google
Your Plugin-Settings: 
 blog|Wordpress software|http://wordpress.com 
 google|Search engine|http://google.com
Result: 
 Welcome to a <a href="http://wordpress.com" title="Wordpress software" rel="nofollow ugc">blog</a> about <a href="http://google.com" title="Search engine" rel="nofollow ugc">google</a>

agLinker

This plugin adds links to specified words in posts and pages.

LaClave

The MasDetalles share plugin to help people share, bookmark, and email your posts and pages using Masdetalles share. New: MasDetalles share.
MasDetalles Share le permite compartir sus enlaces en el marcador social Masdetalles.do desde su blog, email, tienda virtual, y cualquier pagina web.

Masdetalles Share

Help people share, bookmark, and email your posts, pages, your favorite links through MasDetalles.do

agLinker vs Masdetalles Share